[MEncoder-users] Separating each of the 6 channels of ac3 file into separate wav files

[socke]

belcampo schrieb:
> socke wrote:
>> L Lee schrieb:
>>> I recently originated a thread about multiplexing, but now I have a
>>> related
>>> question about DVD audio.
>>>
>>> I have developed a method to use MEncoder to transcode some HD h.264
>>> files
>>> to mpeg2. The picture looks really good and the audio sync is close,
>>> just
>>> not quite close enough (for every 2 hours of video, the video component
>>> comes out about a second shorter than the audio).
>>>
>>> I can increase the tempo of the audio file just enough that it
>>> correctly
>>> syncs with the video by incorporating a process to demux, convert
>>> the audio,
>>> a 6 channel (dolby 5.1) ac3 file, into a stereo wav file using a52dec,
>>> change the tempo using SoX (the most recent version of which is quite
>>> robust), convert back to ac3 with ffmpeg, then re-mux.
>>>
>>> The problem is that the method I just described gives me a stereo
>>> mix-down
>>> of the audio when it is converted to wav, which is fine for most of
>>> the old
>>> video I routinely convert, but now I have some stuff that's newer
>>> and I'd
>>> like to preserve the 6 channels through the tempo change process.
>>>
>>> I'm looking for the simplest possible way to separate those 6
>>> channels into
>>> discrete files, perform the tempo change on each and then combine
>>> them again
>>> into a single ac3 file containing all 6 channels.
>>>
>>> Can MPlayer's dumpaudio option or any other functions of MPlayer and
>>> MEncoder perform any of the conversion parts of the operation?
>>>
>>> I tried using the pan option, then dumpaudio, but the command I used
>>> resulted in a file that still contained all the channels, so it's
>>> clear that
>>> I don't understand the processing steps I'm trying to use:
>>>
>>> mplayer -channels 1 -af pan=1:1:0:0:0:0:0 channel 0 audio.ac3
>>> -dumpaudio
>>> -dumpfile 1-channel.ac3
>>>
>>> Help will be appreciated. Thanks very much!
>>>
>>>   
>> I recently did some ac3 speed change (for conversion between 24000/1001
>> and 25 fps). I used the following pipe to do so:
>>
>> ffmpeg -v 0 -i "$AUDIOFILE" -f sox - \
>> | sox -S -V -p -p speed 1.04270833333333 \
>> | ffmpeg -v 0 -i - -acodec ac3 -ab 448000 -y "$AUDIOFILE2"
>>
>>
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>> MEncoder-users at mplayerhq.hu
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> Whit what version of ffmpeg and sox does this work ? I tried several,
> but get errors like:
> Unknown input or output format: sox
> sox FAIL formats: can't open input  `-': premature EOF
> pipe:: Unknown format
I use...
FFmpeg version SVN-r19742 (I built it some day this month)
SoX v14.3.0